1. Field of the Invention
The present invention relates to a protein composition derived from sesame seed which excels in solubility in water and digestive assimilability, enjoys great practical utility as material for foodstuffs, and fits safe application as material for cosmetic articles and to foodstuffs using the composition.
2. Description of Prior Art
It has been known for long that sesame seed is an excellent food from the nutritional point of view. The sesame seed is used wholly as food in various forms such as roast sesame, ground sesame, roasted dehulled sesame, and pasted sesame. It is otherwise used widely in the form of sesame oil obtained by squeezing or by extraction with solvent.
Though the defatted oil cake which remains after the removal of sesame oil from sesame seed by squeezing or by extraction with solvent has high contents of proteins, carbohydrate, and physiologically active substances all abounding in nutritive value, it finds very little utility for practical applications except feed for domestic animals and fertilizer.
Though the defatted oil cake after the defatting predominantly comprises proteins of high quality, it manifests virtually no solubility in water. The scanty solubility imposes a strict limit on the kinds of applications to be found for the oil cake and the manners of application because it prevents the oil cake from being easily handled while it is being incorporated into foodstuffs and cosmetic articles.
As a means to obtain proteins from sesame seed, the method which collects proteins from oil cake which was roasted and then compressed by subjecting the oil cake to a heat treatment by the use of an acidic aqueous solution (Japanese Unexamined Patent Publication No. 01-206956) may be cited. Since this method collects the proteins from thermally degenerated defatted oil cake by adjusting the oil cake to a pH value of not more than 2, keeping it at or above 70.degree. C. thereby extracting proteins, causing the extracted proteins to precipitate in a neutral zone, and isolating the precipitate, the collected proteins exhibit solubility in water exclusively in an acidic zone and defies solution in neutral water. Further, since the collected proteins themselves are obtained in an undecomposed state, they are at a disadvantage in having a large molecular weight and manifesting no satisfactory digestive assimilability.
For the purpose of decreasing the molecular weight, the method for hydrolyzing the proteins by the use of an enzyme may be conceived. The method disclosed in Japanese Unexamined Patent Publication No. 04-149138 represents a case of hydrolyzing the proteins by simultaneous use of a plurality of enzymes. This method implements the hydrolysis of proteins of soybeans, for example, by simultaneous addition of three kinds of enzymes to the proteins. The product of this hydrolysis principally comprises peptides which have notably low molecular weights averaging in the approximate range of 290-350. It is aimed at fulfilling the function of attaining recovery from fatigue and does not contain physiologically active substances derived from sesame seed. The invention covering this method suggests absolutely nothing about the use of sesame seed as the raw material.
A composition which contains proteins derived from sesame seed, also contains peculiar physiologically active substances derived from sesame seed, and has the proteins principally comprising crude proteins partially converted into peptides and possessing molecular weights distributed in a wide range is expected to excel in solubility in water and digestive assimilability and find extensive utility in applications such as foodstuffs and cosmetic articles. This ideal composition remains yet to be developed.
The subject imposed on the present invention consists in providing a protein composition derived from sesame seed which makes effective use of heretofore unused proteins of sesame seed, contains proteins exhibiting solubility in water unlike the ordinary water-insoluble defatted oil cake, as the proteins principally comprise crude proteins partially converted into peptides and possessing molecular weights distributed in a wide range, and further contains antioxidant precursors such as lignan glycosides and physiologically active substances peculiar to sesame seed such as antioxidant lignans.